[valenterry]

> The only think missing is persistent immutable collections, which are implemented in kotlinx.

You said:

> You have to litter your whole code with `.asScala` and `.asJava`, the java collections don't work with for comprehensions, etc.

So how does kotlinx achieve zero-cost compatibility with Java collections without having something like `.asKotlin` and `.asJava`? Because otherwise there is no difference between Scala and Kotlin in this regards.

[joshlemer]

because the persistentList/Collection/etc in kotlinx implement the appropriate java collection interfaces:

    import java.util.List;

    public class Foo {
        public static void blah(List<Integer> list) {
        }
    }

Kotlin:

    import kotlinx.collections.immutable.persistentListOf

    fun main(): Unit {
        Foo.blah(persistentListOf(1,2,3))
    }

This compiles fine